JP2020153255A - Control device for engine - Google Patents

Abstract

To accurately calculate a volume efficiency coefficient of an engine.SOLUTION: A control device for an engine 2 having an exhaust gas recirculation device and a control unit controlling an exhaust gas recirculation valve on the basis of a load of the engine includes: a target EGR introduction time volume efficiency coefficient calculation section 23 calculating a volume efficiency coefficient woEGR of the engine when an exhaust gas recirculation rate is in a target exhaust gas recirculation state; a volume efficiency coefficient correction EGR rate calculation section 25 calculating an EGR rate b in the target exhaust gas recirculation state; a cylinder internal EGR rate calculation section 26 calculating a current EGR rate a; and a volume efficiency coefficient calculation section 27 calculating a current volume efficiency coefficient Kve1 of the engine by correcting the volume efficiency coefficient wEGR in the target exhaust gas recirculation state, on the basis of a ratio between the current EGR rate a and the EGR rate b in the target exhaust gas recirculation state.SELECTED DRAWING: Figure 4

Description

The present invention relates to a control technique for an engine including an exhaust recirculation device.

In order to properly control the fuel injection of the engine, it is necessary to accurately calculate the amount of intake air into the cylinder. The amount of intake air into the cylinder can be measured using, for example, a flow sensor provided upstream of the intake throttle valve, or estimated from the intake manifold pressure and engine rotation speed, which are the intake pressure on the downstream side of the throttle valve. There is a known way to do it.
Further, in Patent Document 1, during steady operation of the engine, the intake amount into the cylinder is calculated using the intake manifold pressure and the volumetric efficiency equivalent value, and the relationship between the throttle opening and the intake amount is learned, and the transition is made. It is disclosed that the amount of intake air into the cylinder is calculated using the learning result during operation.

Japanese Unexamined Patent Publication No. 2014-84417

However, many engines are equipped with an EGR device (exhaust gas recirculation device) in order to reduce NOx emissions or improve fuel efficiency. The EGR device returns a part of the exhaust gas of the engine to the intake side to lower the combustion temperature in the cylinder, thereby reducing NOx emissions, reducing pumping loss, and improving fuel efficiency. Therefore, when the exhaust gas is recirculated by the EGR device, the amount of fresh air in the cylinder, which is the amount of air that contributes to combustion, decreases, and the amount of intake air (new air amount) in the cylinder required for fuel control is accurate. It becomes difficult to calculate.

In particular, the EGR device is on / off controlled so as to have an exhaust gas recirculation rate set based on, for example, the intake amount, but the exhaust gas recirculation rate changes when the exhaust gas recirculation is switched on / off as in transient operation. , Not only may it be smaller than the exhaust gas recirculation rate set based on the intake amount, but it may also be large immediately after switching, making it difficult to accurately calculate the intake amount into the cylinder. turn into.

The present invention has been made to solve such a problem, and it is possible to accurately calculate the intake air amount in a wide range of situations even if the exhaust is recirculated in an engine equipped with an exhaust recirculation device. Is to provide a control device for the engine.

In order to achieve the above object, the engine control device of the present invention includes an exhaust recirculation path for returning a part of the exhaust of the engine to the intake passage, an exhaust recirculation valve for opening and closing the exhaust recirculation path, and the engine. An engine control device including an exhaust recirculation control unit that controls the exhaust recirculation valve based on an operating state, and a target in which an exhaust recirculation rate by the exhaust recirculation path is set based on the operating state of the engine. The target volumetric efficiency coefficient calculation unit that calculates the volumetric efficiency coefficient of the engine in the target exhaust recirculation state, which is the exhaust recirculation rate, and the target exhaust recirculation rate that calculates the exhaust recirculation rate in the target exhaust recirculation state. Based on the calculation unit, the current exhaust recirculation rate calculation unit that calculates the current exhaust recirculation rate based on the operating state of the engine, and the ratio of the current exhaust recirculation rate to the exhaust recirculation rate in the target exhaust recirculation state. The engine is provided with a first volumetric efficiency coefficient calculation unit that corrects the volumetric efficiency coefficient in the target exhaust recirculation state and calculates the current volumetric efficiency coefficient of the engine.

As a result, the volumetric efficiency coefficient in the target exhaust recirculation state is corrected based on the ratio of the current exhaust recirculation rate to the exhaust recirculation rate in the target exhaust recirculation state, and the current volumetric efficiency coefficient of the engine is calculated. Therefore, the volumetric efficiency coefficient can be calculated accurately even in an exhaust recirculation state other than the target exhaust recirculation state.
Further, preferably, the first volumetric efficiency coefficient calculation unit sets the current exhaust recirculation rate as a, the exhaust recirculation rate in the target exhaust recirculation state as b, and the volumetric efficiency coefficient in the target exhaust recirculation state as wEGR. In this case, the volumetric efficiency coefficient Kve1 of the first current engine may be calculated by Kve1 = wEGR × (1 + b) / (1 + a).

As a result, the volumetric efficiency coefficient of the engine in the exhaust recirculation state other than the target exhaust recirculation state can be easily and accurately calculated based on the ratio of the current exhaust recirculation rate and the exhaust recirculation rate in the target exhaust recirculation state. It will be possible.
Further, preferably, the engine rotation speed detector for detecting the rotation speed of the engine and the intake pressure detector for detecting the intake pressure of the engine are provided, and the target exhaust recirculation volumetric efficiency coefficient calculation unit is described as described above. The volumetric efficiency coefficient of the engine in the target exhaust recirculation state may be calculated based on the rotation speed of the engine and the intake pressure.

As a result, the volumetric efficiency coefficient calculation unit at the time of target exhaust gas recirculation can easily calculate the volumetric efficiency coefficient of the engine in the target exhaust gas recirculation state by using the rotation speed of the engine and the intake pressure.
Further, preferably, the volumetric efficiency coefficient calculation unit at the time of non-exhaust recirculation for calculating the volumetric efficiency coefficient of the engine in the non-exhaust recirculation state where the exhaust recirculation rate is 0, the exhaust recirculation rate in the target exhaust recirculation state, and the above. Based on the ratio with the current exhaust recirculation rate, the volumetric efficiency coefficient in the target exhaust recirculation state and the volumetric efficiency coefficient in the non-exhaust recirculation state are interpolated to obtain the current volumetric efficiency coefficient of the engine. A second volumetric efficiency coefficient calculation unit for calculation is provided, and when the current exhaust recirculation rate is equal to or higher than the exhaust recirculation rate in the target exhaust recirculation state, the first volumetric efficiency coefficient calculation unit is used. The current volumetric efficiency coefficient of the engine is calculated, and when the current exhaust recirculation rate is less than the exhaust recirculation rate in the target exhaust recirculation state, the second volumetric efficiency coefficient calculation unit uses the current engine. It is advisable to calculate the volumetric efficiency coefficient of.

As a result, when the current exhaust recirculation rate is less than the exhaust recirculation rate in the target exhaust recirculation state, the volumetric efficiency coefficient in the target exhaust recirculation state and the volume in the non-exhaust recirculation state are performed by the second volumetric efficiency coefficient calculation unit. The current volumetric efficiency coefficient is calculated accurately between the efficiency coefficient and the efficiency coefficient. On the other hand, when the current exhaust recirculation rate is equal to or higher than the exhaust recirculation rate in the target exhaust recirculation state, the volumetric efficiency coefficient of the current engine is calculated by the first volumetric efficiency coefficient calculation unit, so that a wide range of exhaust recirculation rates can be used. The current volumetric efficiency coefficient can be calculated.

Preferably, the second volumetric efficiency coefficient calculation unit sets the current exhaust recirculation rate as a, the exhaust recirculation rate in the target exhaust recirculation state as b, and the volumetric efficiency coefficient in the target exhaust recirculation state as wEGR. When the volumetric efficiency coefficient in the exhaust recirculation state is woEGR, the volumetric efficiency coefficient Kve2 of the current engine is set by Kve2 = (wEGR × (a / b) + (woEGR × (1- (a / b))). It is good to calculate.

As a result, when the current exhaust return rate is less than the exhaust return rate in the target exhaust return state, the volumetric efficiency coefficient of the engine in the exhaust return state other than the target exhaust return state is set to the exhaust return rate in the target exhaust return state. It is possible to easily calculate based on the ratio with the exhaust return rate of.

According to the engine control device of the present invention, the volumetric efficiency coefficient can be calculated accurately even in an exhaust recirculation state other than the target exhaust recirculation state, so that in a transient operation state such as immediately after switching the exhaust recirculation valve. Also, the volumetric efficiency coefficient can be calculated accurately, and the amount of fresh air sucked into the cylinder can be calculated accurately. As a result, it is possible to accurately control the fuel supply amount according to the intake amount of fresh air, and it is possible to improve fuel efficiency or reduce exhaust gas.

It is a schematic block diagram of the control device of the engine in embodiment of this invention. This is an example of a map showing the relationship between the engine load and the EGR rate. This is an example of a map showing the relationship between the engine load and the volumetric efficiency coefficient. It is a block diagram which shows the structure of the volumetric efficiency coefficient calculation unit of 1st Embodiment in an engine control unit. This is an example of a map showing the relationship between the EGR ratio and the volumetric efficiency coefficient with respect to the engine load in the first embodiment. It is a block diagram which shows the structure of the volumetric efficiency coefficient calculation unit of the 2nd Embodiment in an engine control unit. This is an example of a map showing the relationship between the EGR ratio, the intake manifold pressure, and the volumetric efficiency coefficient with respect to the engine load in the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an engine 2 to which the control device 1 of the present invention is applied.
The engine 2 is mounted on a vehicle as a traveling drive source, and is, for example, a multi-cylinder gasoline engine. In FIG. 1, only one cylinder is briefly described. The engine 2 injects fuel into the intake port of each cylinder at an arbitrary injection timing and injection amount from the fuel injection valve 3 provided in each cylinder, and ignites the air-fuel mixture in the combustion chamber 5 by the spark plug 4. It has a structure that can be burned.

An electronically controlled throttle valve 7 for adjusting the flow rate of fresh air is provided in the intake passage 6 of the engine 2.
Further, the engine 2 is provided with an EGR device 10. The EGR device 10 is composed of an EGR passage 11 (exhaust gas recirculation path) that connects the intake passage 6 and the exhaust passage 8 of the engine 2 and an EGR valve 12 (exhaust gas recirculation valve) that opens and closes the EGR passage 11. The EGR device 10 returns a part of the exhaust gas from the exhaust passage 8 to the intake passage 6 via the EGR passage 11. By allowing a part of the exhaust gas (EGR gas) to flow into the intake passage 6 in this way, the combustion temperature in the cylinder is lowered, the amount of NOx emitted from the engine 2 is reduced, and the fuel consumption is improved.

Further, the engine 2 is provided with a rotation speed sensor 15 (engine rotation speed detector) that detects the rotation speed of the engine 2. The intake manifold 17, which is the end of the intake passage 6 on the engine 2 side, is provided with an intake manifold pressure sensor 18 (intake pressure detector) that detects the intake air pressure (intake pressure). Further, the EGR valve 12 is provided with an EGR opening sensor 19 that detects the opening degree of the EGR valve.

The engine control unit 20 (exhaust gas recirculation control unit) includes an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a timer, a central processing unit (CPU), and the like. The detection information of various sensors such as the in-mani pressure sensor 18 and the EGR opening sensor 19 is input, and the volume efficiency coefficient is calculated based on the various information. The volumetric efficiency coefficient is an index of the ease with which fresh air can enter the cylinder from the intake passage 6, and the cylinder sucks in the amount of air when the air having the same density as that in the intake pipe fills the stroke volume. It is the ratio of the amount of air that has been removed.

The engine control unit 20 further calculates the intake amount of fresh air into the cylinder using the volumetric efficiency coefficient, calculates the fuel injection amount of each cylinder based on the intake amount, and outputs the fuel injection amount from the fuel injection valve 3. Control fuel injection. Further, the engine control unit 20 controls the operation of the engine 2 by controlling the ignition by the spark plug 4, the opening degree of the electronically controlled throttle valve 7, and the opening degree of the EGR valve 12.

FIG. 2 is an example of a map showing the relationship between the load of the engine 2 and the EGR rate. FIG. 3 is an example of a map showing the relationship between the load of the engine 2 and the volumetric efficiency coefficient.
The engine control unit 20 sets a target EGR rate (target exhaust gas recirculation rate) based on the load of the engine 2 and controls the opening degree of the EGR valve 12. The EGR rate (exhaust gas recirculation rate) is the ratio of the flow rate of EGR gas to the flow rate of fresh air. The load of the engine 2 may be calculated based on, for example, the engine rotation speed detected by the rotation speed sensor 15 and the intake manifold pressure detected by the intake manifold pressure sensor 18.

For example, as shown in FIG. 2, the target EGR rate is set to change based on the load of the engine 2, decrease at low load and high load, and increase at medium load. This is to ensure the combustion stability of the engine 2 at a low load, and because the intake manifold pressure rises at a high load, it becomes difficult for the exhaust gas to return.
Further, the volumetric efficiency coefficient of the engine 2 changes according to the load. For example, as shown in FIG. 3, the volumetric efficiency coefficient increases as the load on the engine 2 increases. In addition, the volumetric efficiency coefficient becomes a different value when EGR is not introduced and when EGR is introduced, and when the target EGR is introduced (target exhaust gas recirculation state) when EGR is introduced at the target EGR rate, the proportion of exhaust gas during intake increases. Therefore, the value is smaller than that when EGR is not introduced (non-exhaust gas recirculation state).

Next, a method of calculating the volumetric efficiency coefficient at the time of introducing EGR according to the first embodiment of the present invention will be described with reference to FIGS. 4 and 5. The engine control unit 20 of the present embodiment calculates the volumetric efficiency coefficient not only when the EGR is not introduced and when the target EGR is introduced, but also when the EGR is introduced, which is not the target EGR rate.
FIG. 4 is a block diagram showing the configuration of the volumetric efficiency coefficient calculation unit 21 of the first embodiment in the engine control unit 20. FIG. 5 is an example of a map showing the relationship between the EGR rate and the volumetric efficiency coefficient with respect to the load of the engine 2 in the first embodiment, and the solid line shows the time when the target EGR rate is introduced. The map of the EGR rate in FIG. 5 corresponds to FIG. 2, and the map of the volumetric efficiency coefficient corresponds to the map at the time of introducing the target EGR in FIG.

As shown in FIG. 4, the engine control unit 20 is used as a volumetric efficiency coefficient calculation unit 21 for calculating the volumetric efficiency coefficient Kve in the current operating state (current operating point) of the engine 2, and the volumetric efficiency coefficient is calculated when the target EGR is introduced. Unit 23 (target exhaust gas recirculation volumetric efficiency coefficient calculation unit), in-cylinder air volume calculation unit 24 (target exhaust gas recirculation rate calculation unit), volumetric efficiency coefficient correction EGR rate calculation unit 25 (target exhaust gas recirculation exhaust gas recirculation) A rate calculation unit), an in-cylinder EGR rate calculation unit 26 (current exhaust gas recirculation rate calculation unit), and a volumetric efficiency coefficient calculation unit 27 (first volumetric efficiency coefficient calculation unit) are provided.

The volumetric efficiency coefficient calculation unit 23 at the time of introducing the target EGR confirms and stores in advance by a test or the like based on the intake manifold pressure Pb input from the intake manifold pressure sensor 18 and the engine rotation speed Ne input from the rotation speed sensor 15. The volumetric efficiency coefficient wEGR at the time of introducing the target EGR is calculated using the existing map.
When the target EGR is introduced, the relationship between the load and the intake manifold pressure increases, for example, when the engine speed Ne is constant, the intake manifold pressure increases as the load increases. Then, using the map provided for each engine rotation speed Ne, the volumetric efficiency coefficient wEGR at the time of EGR introduction is obtained based on the load f corresponding to the intake manifold pressure Pb input from the intake manifold pressure sensor 18.

The in-cylinder air amount calculation unit 24 is based on the volumetric efficiency coefficient wEGR at the time of introduction of the target EGR rate calculated by the volumetric efficiency coefficient calculation unit 23 at the time of introduction of the target EGR and the intake manifold pressure Pb input from the intake manifold pressure sensor 18, and the target EGR rate. Calculate the load (filling efficiency Ec) at the time of introduction. The load (filling efficiency Ec) may be calculated by, for example, the following equation (1).
Load (filling efficiency Ec) = wEGR x (Pb / atmospheric pressure) x 100 (%) ... (1)
The EGR rate calculation unit 25 for correcting the volumetric efficiency coefficient is the volumetric efficiency which is the EGR rate at the time of introduction of the target EGR based on the load (filling efficiency Ec) calculated by the in-cylinder air amount calculation unit 24 and the engine rotation speed Ne. The EGR rate b for coefficient correction (exhaust gas recirculation rate in the target exhaust gas recirculation state) is calculated.

The in-cylinder EGR rate calculation unit 26 uses the engine rotation speed Ne input from the rotation speed sensor 15, the intake manifold pressure Pb input from the intake manifold pressure sensor 18, and the opening degree θegr of the EGR valve 12 input from the EGR opening sensor 19. Based on this, for example, the EGR rate a (current exhaust gas recirculation rate) at the current operating point is calculated using a map stored in advance.
The volumetric efficiency coefficient calculation unit 27 has a volumetric efficiency coefficient wEGR calculated by the volumetric efficiency coefficient calculation unit 23 at the time of introduction of the target EGR and an EGR rate calculation unit 25 at the time of introduction of the target EGR calculated by the volumetric efficiency coefficient correction EGR rate calculation unit 25. The volumetric efficiency coefficient kve1 at the current operating point is calculated based on the EGR rate b and the EGR rate a at the current operating point calculated by the in-cylinder EGR rate calculating unit 26.

The volumetric efficiency coefficient Kve1 at the current operating point is calculated by the following equation (2).
Kve1 = wEGR × (1 + b) / (1 + a) ... (2)
Then, the calculated volumetric efficiency coefficient Kve1 is defined as the volumetric efficiency coefficient Kve at the current operating point.
As described above, the volumetric efficiency coefficient wEGR at the time of introducing the target EGR rate is corrected, and the volumetric efficiency coefficient kve used for calculating the intake amount of the engine 2 is calculated.

As the volumetric efficiency coefficient kve used to calculate the intake amount of the engine 2, the volumetric efficiency coefficient wEGR at the time of introducing the target EGR rate is usually used. However, when EGR is not introduced, the volumetric efficiency coefficient Kve is higher than the volumetric efficiency coefficient wEGR when the target EGR rate is introduced. Immediately after the EGR valve 12 is switched from non-introduction (closed) to introduced (open), the EGR rate momentarily becomes larger than the target EGR rate, and the volumetric efficiency coefficient Kve is the volume at the time of introduction of the target EGR rate. It may be smaller than the efficiency coefficient wEGR.

On the other hand, in the present embodiment, the volumetric efficiency coefficient wEGR at the time of introducing the target EGR rate is corrected by the ratio of the EGR rate a at the current operation point to the EGR rate b at the time of introducing the target EGR, and the current operation is performed. Find the volumetric efficiency coefficient Kve1 at the point.
Specifically, the volumetric efficiency coefficient calculation unit 27 calculates the volumetric efficiency coefficient Kve of the current engine by the calculation of Kve = Kve1 = wEGR × (1 + b) / (1 + a), so that the volumetric efficiency coefficient Kve of the current engine can be easily obtained. It can be obtained accurately and accurately.

In particular, when the EGR rate a at the current operating point is higher than the EGR rate b at the time of introducing the target EGR, the volumetric efficiency coefficient Kve1 at the current operating point is lower than the volumetric efficiency coefficient wEGR at the time of introducing the target EGR rate. However, in such a case, the volumetric efficiency coefficient Kve1 at the current operating point can be obtained with high accuracy.
On the other hand, when the EGR rate a at the current operating point is lower than the EGR rate b at the time of introducing the target EGR, the volumetric efficiency coefficient Kve1 at the current operating point is higher than the volumetric efficiency coefficient wEGR at the time of introducing the target EGR rate. However, even in such a case, the volumetric efficiency coefficient Kve1 at the current operating point can be obtained with high accuracy.

As a result, even in a situation where the opening degree of the EGR valve 12 is changing as in the transient operation state of the engine 2, the volumetric efficiency coefficient Kve (= Kve1) is used to accurately inhale the amount of fresh air into the cylinder. It can be calculated, and the fuel supply amount can be accurately controlled based on the intake amount of the fresh air, and the fuel consumption can be improved.
Next, a method of calculating the volumetric efficiency coefficient at the time of introducing EGR according to the second embodiment of the present invention will be described with reference to FIGS. 6 and 7.

FIG. 6 is a block diagram of the volumetric efficiency coefficient calculation unit 31 of the second embodiment in the engine control unit 20. FIG. 7 is an example of a map showing the relationship between the EGR rate, the intake manifold pressure, and the volumetric efficiency coefficient with respect to the load of the engine 2 in the second embodiment. The solid line shows the target EGR rate when the target EGR rate is introduced, and the broken line shows the EGR not introduced. .. The map of the EGR rate in FIG. 7 corresponds to FIG. 2, and the map of the volumetric efficiency coefficient corresponds to FIG.

As shown in FIG. 6, the volumetric efficiency coefficient calculation unit 31 of the second embodiment has a volumetric efficiency coefficient calculation unit 22 (non-exhaust) with respect to the volumetric efficiency coefficient calculation unit 21 of the first embodiment when EGR is not introduced. It also has a volumetric efficiency coefficient calculation unit during recirculation).
The volumetric efficiency coefficient calculation unit 22 when the EGR is not introduced confirms and stores in advance by a test or the like based on the intake manifold pressure Pb input from the intake manifold pressure sensor 18 and the engine rotation speed Ne input from the rotation speed sensor 15. The volumetric efficiency coefficient woGR when EGR is not introduced is calculated using the map.

Regarding the relationship between the load and the intake manifold pressure, for example, when the engine rotation speed Ne is constant, as shown by the broken line c in FIG. 7, the intake manifold pressure increases as the load increases when EGR is not introduced. It becomes a proportional relationship. Then, using the map provided for each engine rotation speed Ne, the volumetric efficiency coefficient woGR when EGR is not introduced is obtained based on the load d corresponding to the intake manifold pressure Pb. On the other hand, when the engine speed Ne is constant, the load f when the target EGR is introduced is smaller than the load d when the target EGR is not introduced, so that the volumetric efficiency coefficient wEGR when the target EGR is introduced is the time when the EGR is not introduced. The value is smaller than the volumetric efficiency coefficient woGR.

The volumetric efficiency coefficient calculation unit 32 (first volumetric efficiency coefficient calculation unit, second volumetric efficiency coefficient calculation unit) in the second embodiment is the EGR rate at the current operating point calculated by the in-cylinder EGR rate calculation unit 26. The calculation method of the volumetric efficiency coefficient Kve is switched based on a and the EGR rate b at the time of introduction of the target EGR calculated by the volumetric efficiency coefficient correction EGR rate calculation unit 25.
When the EGR rate a at the current operating point is equal to or greater than the EGR rate b at the time of introducing the target EGR, the EGR rate a at the current operating point and the EGR rate b at the time of introducing the target EGR as in the first embodiment are described above. And the volumetric efficiency coefficient Kve1 at the current operating point calculated based on the volumetric efficiency coefficient wEGR at the time of introducing the target EGR rate is defined as the volumetric efficiency coefficient Kve. On the other hand, when the EGR rate a at the current operating point is less than the EGR rate b at the time of introducing the target EGR, the EGR rate a at the operating point, the EGR rate b at the time of introducing the target EGR, and the volumetric efficiency at the time of introducing the target EGR rate. The volumetric efficiency coefficient Kve2 at the current operating point is calculated based on the coefficient wEGR and the volumetric efficiency coefficient woGR when EGR is not introduced, which is calculated by the volumetric efficiency coefficient calculation unit 22 when EGR is not introduced, and the volumetric efficiency coefficient Kve2 is calculated. Let be the volumetric efficiency coefficient Kve. In the volumetric efficiency coefficient calculation unit 32, the function of calculating the volumetric efficiency coefficient Kve1 at the current operating point corresponds to the first volumetric efficiency coefficient calculation unit of the present invention, and the volumetric efficiency coefficient Kve2 at the current operating point is calculated. The function to perform corresponds to the second volumetric efficiency coefficient calculation unit of the present invention.

The volumetric efficiency coefficient Kve2 at the current operating point is calculated by the following equation (3).
Kve2 = wEGR × (a / b) + (woEGR × (1- (a / b)) ... (3)
Then, the calculated volumetric efficiency coefficient Kve1 is defined as the volumetric efficiency coefficient Kve at the current operating point.
As described above, in the second embodiment, when the EGR rate a at the current operating point is equal to or higher than the EGR rate b at the time of introducing the target EGR, the volumetric efficiency coefficient Kve is set as in the first embodiment. When the EGR rate a at the current operating point is less than the EGR rate b at the time of introducing the target EGR, the volumetric efficiency coefficient wEGR at the time of not introducing the EGR is added to calculate the volumetric efficiency coefficient Kve.

For example, immediately after switching the EGR valve 12 between non-introduction (closed valve) and introduction (open valve), the volumetric efficiency coefficient is the value wEGR when EGR is not introduced and the value wEGR when the target EGR rate is introduced. When the interval is changed, the volumetric efficiency coefficient becomes a value different from the value wEGR when the target EGR rate is introduced and the value woGR when EGR is not introduced.
On the other hand, in the present embodiment, when the EGR rate a at the current operating point is less than the EGR rate b at the time of introducing the target EGR, the volumetric efficiency coefficient woGR when the EGR is not introduced and the volumetric efficiency at the time of introducing the target EGR The volumetric efficiency coefficient Kve2 at the time of low EGR introduction is calculated by interpolating the coefficient wEGR.

Specifically, the volumetric efficiency coefficient woGR when EGR is not introduced and the volumetric efficiency coefficient wEGR when the target EGR rate is introduced are calculated from the immunity pressure Pb and the engine rotation speed Ne, which represent the current operating points of the engine 2, respectively. Instead of selecting between EGR introduction and non-introduction and using it as the volumetric efficiency coefficient Kve2 at the current operating point, it corresponds to the ratio of the EGR rate b at the time of introducing the target EGR and the EGR rate a at the current operating point. Then, the current volumetric efficiency coefficient Kve2 is set as a value between the volumetric efficiency coefficient woGR when EGR is not introduced and the volumetric efficiency coefficient wEGR when the target EGR is introduced.

In this way, the volumetric efficiency coefficient Kve2 when EGR is low is set to a value between the volumetric efficiency coefficient woGR when EGR is not introduced and the volumetric efficiency coefficient wEGR when EGR is introduced, based on the operating state of the engine 2. Even in a situation where the EGR rate at the current operating point is not the target EGR rate, the volumetric efficiency coefficient Kve2 can be calculated accurately.
As a result, when the EGR coefficient a at the current operating point is less than the EGR coefficient b at the time of introducing the target EGR, for example, immediately after switching the EGR valve 12 between non-introduction (closed valve) and introduction (open valve). As described above, the volumetric efficiency coefficient Kve2 can be calculated accurately in a state where the volumetric efficiency coefficient changes between the value woGR when EGR is not introduced and the value wEGR when the target EGR rate is introduced.

Further, the volumetric efficiency coefficient calculation unit 32 determines that Kve = Kve2 = (wEGR × (a / b) + (woEGR × (1)) when the EGR rate a at the current operating point is less than the EGR rate b at the time of introducing the target EGR. Since the volumetric efficiency coefficient Kve of the current engine is calculated by the calculation of − (a / b))), the volumetric efficiency coefficient Kve of the current engine can be easily and accurately obtained.
In this way, when the volumetric efficiency coefficient Kve2 is set between the volumetric efficiency coefficient woeGR when EGR is not introduced and the volumetric efficiency coefficient wEGR when the target EGR is introduced, the EGR rate b when the target EGR is introduced and the current operating point are used. By using the ratio (a / b) of EGR to EGR rate a, a weighted average with an appropriate weight is taken between the volumetric efficiency coefficient w EGR when EGR is not introduced and the volumetric efficiency coefficient wEGR when EGR is introduced. , The volumetric efficiency coefficient Kve2 of the current engine can be calculated more accurately.

Then, in a situation where the opening degree of the EGR valve 12 is changing as in the transient operation state of the engine 2, the amount of fresh air sucked into the cylinder can be calculated more accurately using the volumetric efficiency coefficient Kve. , The fuel supply amount can be controlled more accurately based on the intake amount of the fresh air, and the fuel consumption can be further improved.
If the EGR rate a at the current operating point is equal to or greater than the EGR rate b at the time of introduction of the target EGR, the volumetric efficiency coefficient Kve1 is calculated and the volumetric efficiency coefficient Kve is used to obtain the volumetric efficiency coefficient Kve in a wide range. It can be calculated accurately.

The invention of the present application is not limited to the above embodiment.
For example, in the above embodiment, the volumetric efficiency coefficient calculation unit 22 when EGR is not introduced and the volumetric efficiency coefficient calculation unit 23 when target EGR is introduced calculate the volumetric efficiency coefficient woGR or wEGR using the rotation speed Ne of the engine 2 and the intake manifold pressure Pb. However, the load of the engine 2 or an index corresponding to the load may be used instead for the calculation.

Further, in the present embodiment, the present invention is applied to a gasoline engine that injects fuel into an intake port, but an EGR device such as an engine that injects fuel into a cylinder, a diesel engine that compresses and ignites, or the like is provided. The present invention can be widely applied to various engines.

2 Engine 11 EGR passage (exhaust gas recirculation path)
13 EGR valve (exhaust gas recirculation valve)
15 Rotation speed sensor (engine rotation speed detector)
18 Manifold pressure sensor (intake pressure detector)
20 Engine control unit (exhaust recirculation control unit)
22 Volumetric efficiency coefficient calculation unit when EGR is not introduced (Volume efficiency coefficient calculation unit when non-exhaust gas recirculation)
23 Volumetric efficiency coefficient calculation unit when target EGR is introduced (Volume efficiency coefficient calculation unit when target exhaust gas recirculation)
24 In-cylinder air amount calculation unit (exhaust recirculation rate calculation unit at target exhaust recirculation)
25 EGR rate calculation unit for volumetric efficiency coefficient correction (exhaust gas recirculation rate calculation unit at target exhaust gas recirculation)
26 In-cylinder EGR rate calculation unit (current exhaust gas recirculation rate calculation unit)
27 Volumetric efficiency coefficient calculation unit (first volumetric efficiency coefficient calculation unit)
32 Volumetric efficiency coefficient calculation unit (first volumetric efficiency coefficient calculation unit, second volumetric efficiency coefficient calculation unit)

Claims (5)

An exhaust return path that returns a part of the exhaust gas of the engine to the intake passage, an exhaust return valve that opens and closes the exhaust return path, and an exhaust return control unit that controls the exhaust return valve based on the operating state of the engine. It is an engine control device equipped with
Target exhaust recirculation volumetric efficiency coefficient calculation unit for calculating the volumetric efficiency coefficient of the engine in the target exhaust recirculation state, which is the target exhaust recirculation rate set based on the operating state of the engine. When,
The exhaust recirculation rate calculation unit at the time of target exhaust recirculation, which calculates the exhaust recirculation rate in the target exhaust recirculation state,
The current exhaust recirculation rate calculation unit that calculates the current exhaust recirculation rate based on the operating state of the engine,
Based on the ratio of the current exhaust recirculation rate to the exhaust recirculation rate in the target exhaust recirculation state, the volumetric efficiency coefficient in the target exhaust recirculation state is corrected to calculate the current volumetric efficiency coefficient of the engine. An engine control device including a first volumetric efficiency coefficient calculation unit. When the current exhaust gas return rate is a, the exhaust return rate in the target exhaust return state is b, and the volumetric efficiency coefficient in the target exhaust return state is wEGR, the first volumetric efficiency coefficient calculation unit
Kve1 = wEGR × (1 + b) / (1 + a)
The engine control device according to claim 1, wherein the volumetric efficiency coefficient Kve1 of the current engine is calculated. An engine rotation speed detector that detects the rotation speed of the engine,
An intake pressure detector for detecting the intake pressure of the engine is provided.
The target exhaust recirculation volumetric efficiency coefficient calculation unit calculates the volumetric efficiency coefficient of the engine in the target exhaust recirculation state based on the rotation speed of the engine and the intake pressure. 2. The engine control device according to 2. A volumetric efficiency coefficient calculation unit for non-exhaust recirculation that calculates the volumetric efficiency coefficient of the engine in a non-exhaust recirculation state in which the exhaust recirculation rate is 0,
Based on the ratio of the exhaust recirculation rate in the target exhaust recirculation state to the current exhaust recirculation rate, the volumetric efficiency coefficient in the target exhaust recirculation state and the volumetric efficiency coefficient in the non-exhaust recirculation state are interpolated. A second volumetric efficiency coefficient calculation unit for calculating the volumetric efficiency coefficient of the current engine is provided.
When the current exhaust recirculation rate is equal to or higher than the exhaust recirculation rate in the target exhaust recirculation state, the first volumetric efficiency coefficient calculation unit calculates the current volumetric efficiency coefficient of the engine.
When the current exhaust recirculation rate is less than the exhaust recirculation rate in the target exhaust recirculation state, the second volumetric efficiency coefficient calculation unit calculates the current volumetric efficiency coefficient of the engine. The engine control device according to any one of claims 1 to 3. The second volumetric efficiency coefficient calculation unit sets the current exhaust recirculation rate as a, the exhaust recirculation rate in the target exhaust recirculation state as b, the volumetric efficiency coefficient in the target exhaust recirculation state as wEGR, and the non-exhaust recirculation state. When the volumetric efficiency coefficient in is woEGR,
Kve2 = (wEGR × (a / b) + (woEGR × (1- (a / b))))
The engine control device according to claim 4, wherein the volumetric efficiency coefficient Kve2 of the current engine is calculated.

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